Processes by which DNA is transferred from donor to recipient bacterial cell.Just the initial steps in transfer are shown. DNA Transfer in Bacteria Donor Free DNA Recipient Transformation pobb Transduction DNA-containing Viruses Con jugation:Plasmid transfer Plasmid-containing donor Con jugation:Chromosome transfer Donor cell
Processes by which DNA is transferred from donor to recipient bacterial cell. Just the initial steps in transfer are shown. T7012-a.gif T7012-b.gif T7012-c.gif
Complementation When two mutant strains are genetically crossed (mated),homologous recombination can yield a wild- type recombinant unless both of the mutations include changes in exactly the same base pairs. If two different Trp Escherichia coli (strains that require the amino acid tryptophan in the medium)are crossed and Trp recombinants are obtained,it is clear that the mutations in the two strains did not include the same base pairs.However,this experiment cannot detect whether the mutations were in the same gene.This can be determined by a type of experiment called a complementation test
Complementation When two mutant strains are genetically crossed (mated), homologous recombination can yield a wildtype recombinant unless both of the mutations include changes in exactly the same base pairs. If two different Trp− Escherichia coli (strains that require the amino acid tryptophan in the medium) are crossed and Trp − recombinants are obtained, it is clear that the mutations in the two strains did not include the same base pairs. However, this experiment cannot detect whether the mutations were in the same gene. This can be determined by a type of experiment called a complementation test
Wild type cell:both gene are functional and cell is Trp* Mutant x:cell contains mutation 1 and is Trp-(requires tryptophan for growth) Mutant y:cell contains mutation 2 and is Trp Mutant z:cell contains mutation 3 and is Trp- Trans test of mutations 1 and 2: complementation occures (cell is Trp+),therefore mutation are in separate genes Trans test of mutations 2 and 3:no complementation occures (cell is Trp-),therefore mutations are in the same gene
Wild type cell: both gene are functional and cell is Trp+ Mutant x: cell contains mutation 1 and is Trp-(requires tryptophan for growth) Mutant y: cell contains mutation 2 and is Trp - Mutant z: cell contains mutation 3 and is TrpTrans test of mutations 1 and 2: complementation occures (cell is Trp+), therefore mutation are in separate genes Trans test of mutations 2 and 3: no complementation occures (cell is Trp-), therefore mutations are in the same gene
Three main processes of genetic recombination in prokaryotes fragments of homologous DNA from a donor chromosome are transferred to a recipient cell (1)Transformation,which involves donor DNA free in the environment (2)Transduction,in which the donor DNA transfer is mediated by a virus (3)Conjugation,in which the transfer involves cell- to-cell contact and a conjugative plasmid in the donor cell
(1) Transformation, which involves donor DNA free in the environment (2) Transduction, in which the donor DNA transfer is mediated by a virus (3) Conjugation, in which the transfer involves cellto-cell contact and a conjugative plasmid in the donor cell Three main processes of genetic recombination in prokaryotes fragments of homologous DNA from a donor chromosome are transferred to a recipient cell
Transformation Donor Transduction Donor Conjugation Donor pilus Recipient Recipient
Conjugation Transformation Transduction